The species that score the lowest (i.e. most negative) values in variable 4 are epipelagic and marine Rhodobacterales, Rhizobiales, and Rhodospirillales that are capable of utilizing a broad spectrum of carbon sources [1]}. Here the most significant metabolic reactions are all involved in the L-2-aminoadipate pathway of lysine synthesis [2]} and the production of L-pipecolic acid (Table S5), pointing to a strategy for growth under high-salt conditions [3]}. Our interpretation is that this variable traces a range of strategies spanning a generalist lifestyle in oceans to associations with terrestrial hosts.
